Evolution of Alfven wave-driven solar winds to red giants

TL;DR

This paper presents 1D MHD simulations demonstrating how Alfven waves driven by photospheric motions accelerate solar and red giant stellar winds, revealing structured winds with hot bubbles in red giants.

Contribution

It introduces detailed simulations of Alfven wave-driven winds for both solar and red giant stars, highlighting the mechanisms of wave dissipation and wind structuring.

Findings

Alfven waves dissipate via 3-wave coupling and mode conversion.

Photospheric fluctuations naturally drive coronal heating and solar wind acceleration.

Red giant winds are highly structured with hot bubbles embedded in cool material.

Abstract

In this talk we introduce our recent results of global 1D MHD simulations for the acceleration of solar and stellar winds. We impose transverse photospheric motions corresponding to the granulations, which generate outgoing Alfven waves. The Alfven waves effectively dissipate by 3-wave coupling and direct mode conversion to compressive waves in density-stratified atmosphere. We show that the coronal heating and the solar wind acceleration in the open magnetic field regions are natural consequence of the footpoint fluctuations of the magnetic fields at the surface (photosphere). We also discuss winds from red giant stars driven by \Alfven waves, focusing on different aspects from the solar wind. We show that red giants wind are highly structured with intermittent magnetized hot bubbles embedded in cool chromospheric material.